This invention relates to methods of fabricating input/output terminals (I/O terminals) on input/output pads (I/O pads) of an electronic component.
In the prior art, many types of electronic components exist which include I/O terminals on I/O pads as a means of sending electrical signals to and receiving electrical signals from other circuitry within the component. For example, I/O terminals on I/O pads are commonly provided on a single chip ceramic integrated circuit package. Such a package is made of several layers of ceramic which are integrated together in a stack. Running on and through those layers are microscopic conductors which are patterned to carry electrical signals to and from an integrated circuit chip which gets mounted to the package. Some of those conductors connect to I/O pads which are arranged in a pattern on an outer layer of the stack, and a respective I/O terminal extends outward from the stack on each of the I/O pads.
Similarly, I/O terminals on I/O pads are provided on a multichip ceramic integrated circuit package. Such a package has the same structure as described above, except that it is large enough to house multiple integrated circuit chips and patterned conductors which carry signals to, from, and between the chips. Likewise, I/O terminals on I/O pads are provided on an epoxy glass integrated circuit package which is similar to the above described ceramic packages except that the ceramic layers are replaced with epoxy glass layers.
Now a problem which arises with all of the above described electronic components is that in order to integrate the ceramic layers (or epoxy glass layers) together in a stack, those layers must be subjected to high temperatures and pressures; and that inherently causes the layers to shrink. Further, the amount of shrinkage which occurs varies from one package to another. Consequently, after this shrinkage occurs, the I/O pads which are on an outer layer of the stack are not accurately referenced to any of the sides of the stack.
In the prior art, this inaccuracy between the I/O pads and the sides of the stack had to be eliminated before I/O terminals could be fabricated on the I/O pads; and this was achieved by grinding the sides of the stack until the sides were separated from the I/O pads by a certain predetermined distance. Then, the stack could be placed in a jig which enabled the I/O terminals to be aligned with and attached to the I/O pads by referencing the location of the I/O pads and I/O terminals to the edges of the stack.
However, a problem with the above prior art method of attaching I/O terminals to I/O pads is that it requires the sides of each electronic component to be ground very accurately; and that, compared to the overall cost of the electronic component, is an expensive operation. Accordingly, a primary object of the present invention is to provide a novel method of manufacturing I/O terminals on I/O pads in which the above problem is overcome.